1. Field of the Invention
The present invention relates to timing devices for recording the time an apparatus has been operating. More particularly, the invention relates to devices for recording the length of time an engine-driven apparatus has been running.
2. Description of the Related Art
Numerous devices are known in the art for measuring the time an electrically powered or engine driven apparatus has been operating. Exemplary of such devices are those disclosed in the following U.S. Patents.
U.S. Pat. No. 4,624,578 discloses a rental contract timer system for use on rental equipment such as television sets. Rental equipment such as television sets are provided with a timer which operates a relay to connect power to the equipment only during the time for which rental has been paid. The timer includes a magnetic reader head and decoder to produce digital signals corresponding with a magnetic strip which has been encoded with the rental period and identifying information at the location where the rent is paid. The timer contains a real-time clock and microprocessor to compare the current time with the time in the rental period. A power supply for the timer derives energy from the same power lines used for the rental equipment, but a battery is also provided to power the clock alone when the power supply is not energized. Displays of the current time and rental expiration time are provided, as well as visible and audible alarms to warn of the approach of the end of the rental period.
U.S. Pat. No. 4,472,964 discloses an apparatus for indicating the need for maintenance work on an internal combustion engine. The device is equipped, in the manner of an electric clock, with a frequency reducer, an amplifier, a stepping motor, and a clock movement. The frequency reducer, however, does not receive its pulses from a quartz oscillator, as in the case of a quartz clock, but from a pulse generator of a revolution indicator. The pulse generator can, of course, also be a separate component which is intended exclusively for the device.
U.S. Pat. No. 4,290,128 discloses a time sequence monitor having a plurality of signal channels, a plurality of stopwatch circuits and a plurality time lapse displays interconnected so that the relative time lapses in a series of related occurences can be displayed.
U.S. Pat. No. 3,965,669 discloses an engine running time indicator for use with an engine. The running time indicator has a ceramic resonator-controlled oscillator that drives an electronic divider, a multiplexer, and a stepping motor which is connected through a gear train to a mechanical display showing elapsed time. The running time indicator operates only when an electrical generator, which is mechanically coupled with the engine, produces sufficient voltage to operate the indicator circuits. Sufficient voltage is produced at all engine speeds above a threshold speed which is less than engine idling speed. The generator supplies A.C. voltage to a doubler circuit that has two separate outputs-one for supplying large pulses of current for the stepping motor, and a partially isolated second output for other electronic loads. A tachometer output signal is provided at an auxiliary output terminal and is buffered to prevent disablement of the running time indicator by shirt circuits and externally applied voltages at the auxiliary output terminal. The running time indicator is therefore self-powered, relatively secure from tampering, and accurate.
U.S. Pat. No. 1,967,157 discloses a time measuring instrument of the kind in which a clockwork mechanism is adapted to integrate and indicate the total time of operation of an engine, machine, vehicle, aircraft, or the like. The device includes a motor spring, a flexible diaphragm, a spring winding device operatively connected to the time integrating mechanism, a main indicating hand, a loose auxiliary indicating hand mounted concentric with the main hand, a friction clutch for connecting both hands for movement as a unit, the diaphragm being operatively connected to the time integrating mechanism whereby movement of the diaphragm starts and stops the mechanism, the diaphragm being exposed to variable air pressure.
U.S. Pat. No. 1,785,724 discloses an elapsed time register for airplanes which records the length of time an airplane has been flown and the number of hours the motor has operated. The elapsed time register will also start and stop the airplane motor without having any mechanical connection therewith. The registering device includes a housing, a wind tunnel through the housing, an air screw in the tunnel, a guard at the mouth of the tunnel to prevent manipulation of the screw, a registering mechanism driven by the screw, and a device for limiting the rate of rotation of the screw.